17 replies to this topic

[Minigman]

I have issues!

After about 10 minutes of running my rocker cover is filling with oil and spitting out the of both the rocker cover breather and timing cover breather.

It’s a newly built 1330 pre a+ GT block. Spec is good with all new internals.

My engine builder is sure it’s not crankcase pressure as he says the two breathers should be ok.

No smoke coming from anywhere before the oil appears.

The oil was measured to the letter to check dipstick was correct and was bang on the max before start up.

Cam bearings were replaced which if installed incorrrectly would cause the rocker to fill but not sure that would cause the timing cover issue too.

Rings appear ok. Hot pressures are normal and equal.

Anything else to check?

The engine has been built by a well renowned engine builder with 40 years plus experience building a series engines, he also race and rally prepares exotic classics e-types, healeys and fords etc so should know his stuff. But he’s scratching his head a bit.

Any help or suggestions would be appreciated.

[nicklouse]

Oil returns to the sump vis the pushrod holes and the buckets. Not much you can do about that. Timing cover is not fed by any oil other than splash so forget that.

[Minigman]

Oil returns to the sump vis the pushrod holes and the buckets. Not much you can do about that. Timing cover is not fed by any oil other than splash so forget that.

So crankcase pressure is still the best bet then?

[imack]

Oil must be fed into the timing cover via bleed from the crank main bearing shells and the cam bearing, the only way back to the sump from memory is via the two small drillings in the main bearing cap. If these were blocked with sealant the timing cover would fill about 1/2 way before the oil drained back into the sump via the casting hole in the block. If that casting hole is level with the timing cover breather hole the oil level could effectivly block off the timing cover breather preventing it venting properly, then crank case pressure would only be able to vent via the rocker cover. Is it possible that crank case pressure could then be sufficient to prevent oil draining down from the rocker cover and causing it to fill up and oil spit from both breathers?

[Minigman]

Oil must be fed into the timing cover via bleed from the crank main bearing shells and the cam bearing, the only way back to the sump from memory is via the two small drillings in the main bearing cap. If these were blocked with sealant the timing cover would fill about 1/2 way before the oil drained back into the sump via the casting hole in the block. If that casting hole is level with the timing cover breather hole the oil level could effectivly block off the timing cover breather preventing it venting properly, then crank case pressure would only be able to vent via the rocker cover. Is it possible that crank case pressure could then be sufficient to prevent oil draining down from the rocker cover and causing it to fill up and oil spit from both breathers?

Yes that makes sense. So the front cam bearing may well be responsible then by the sounds of it.

[imack]

Oil must be fed into the timing cover via bleed from the crank main bearing shells and the cam bearing, the only way back to the sump from memory is via the two small drillings in the main bearing cap. If these were blocked with sealant the timing cover would fill about 1/2 way before the oil drained back into the sump via the casting hole in the block. If that casting hole is level with the timing cover breather hole the oil level could effectivly block off the timing cover breather preventing it venting properly, then crank case pressure would only be able to vent via the rocker cover. Is it possible that crank case pressure could then be sufficient to prevent oil draining down from the rocker cover and causing it to fill up and oil spit from both breathers?

Yes that makes sense. So the front cam bearing may well be responsible then by the sounds of it.

I'm thinking more that the oil return drillings in the main bearing cap may be blocked.

[mini13]

sounds like the front cam bearing is in the wrong way round, there are grooves in the cam journel and bearing at the timing cover end that send a pulsed feed to the rockers, if its the wrong way round it can be a continuous feed,

[Minigman]

This is a bit of a blast from the past here.

A year on and the cam bearing was indeed in the wrong way round and was reinstalled correctly. At the same time an additional breather was added on the transfer case and the oil filling the rocker cover was over.

Today I’ve noticed that the rocker cover breather is blowing a bit not sucking. Is this normal and to be expected? It’s not blowing oil just vapour.

Time for a catch tank?

Why do people run catch tanks, is it just a race / track requirement? And if so, do race cars suffer from oil escaping the breathers more than a race car would?

[nicklouse]

depends on what your set up is.

 

if all the breathers are "open" the rocker cover breather will have never "sucked".

[Minigman]

depends on what your set up is.

if all the breathers are "open" the rocker cover breather will have never "sucked".

they are open with K&N filters on. So that 3 in all. 1 on the clutch end, 1 on the rocker and the other on the timing cover. The timing cover one always seems more oily than the others.

[nicklouse]

 

depends on what your set up is.

if all the breathers are "open" the rocker cover breather will have never "sucked".

they are open with K&N filters on. So that 3 in all. 1 on the clutch end, 1 on the rocker and the other on the timing cover. The timing cover one always seems more oily than the others.

 

Then it would never suck as there is nothing to suck the gasses out. You are just seeing it breath the same as the others.

[Minigman]

Thanks Nick. Needed the reassurance as this engine hasn’t been the greatest on reliability up to now.

[Ethel]

Race engines have catch cans because, like yours, there's no suction. That comes from the inlet manifold being at part throttle on a road car. Race cars tend to spend as little time as possible at part throttle.

[nicklouse]

Race engines have catch cans because, like yours, there's no suction. That comes from the inlet manifold being at part throttle on a road car. Race cars tend to spend as little time as possible at part throttle.

nope. the reason they have catch cans is because the rules say we have to have them.

 

and they are there just in case the engine decides to puke up some oil it is caught.

[Spider]

 

depends on what your set up is.

if all the breathers are "open" the rocker cover breather will have never "sucked".

they are open with K&N filters on. So that 3 in all. 1 on the clutch end, 1 on the rocker and the other on the timing cover. The timing cover one always seems more oily than the others.

 

 

For a Road Car, I'd suggest either a PCV or preferably a CCV set up. This will also reduce the risk of building up 'Mayo' in the Rocker Cover.